Among the metabolic effects of diabetes mellitus is an abnormality of growth hormone secretion. The growth hormone abnormalities have been proposed as one link between diabetes and its long-term complications. The somatomedins are a group of peptides under growth hormone control which have both insulin-like and growth promoting effects. The relationships between growth hormone, insulin, somatomedin by bioassay and radioreceptor assay, somatomedin plasma binding site, and mononuclear cell receptors for 125-I-insulin and 125 I-Somatomedin will be determined in ambulatory diabetic patients and normal controls. Animal studies will be used to determine the variation of these parameters in varying states of insulin deficiency and excess, with and without growth hormone deficiency. In addition, tissue somatomedin receptors and insulinase activity will be measured. Tissue culture studies will be made on the hormonal control of number and affinity of receptor sites for somatomedin, growth hormone, and insulin. These data will provide further understanding of the consequences of diabetes on the growth hormone-somatomedin system.